Single pass electrographic printers including, by way of example, electrophotographic printers employing xerographic technology having more than one process station which provide sequential images to form a composite image require critical control of the registration of each of the sequenced images. This is particularly true in color printers, which produce each sequence of the composite image separately to form a final multi-color image. Failure to achieve registration of the images yields printed copies which have misaligned pixels. This condition is generally obvious upon viewing of the copy, as such copies usually exhibit fuzzy color separations, bleeding or other errors which make such copies unsuitable for intended uses.
Means to provide a simple, relatively inexpensive, and accurate means to provide proper registration of latent images superposed in such printing systems has been a goal of persons involved in the design, manufacture and use of electrographic printers. This need has been particularly recognized by those in the color and highlight color portion of the xerography art, the need for such a means to provide accurate and inexpensive registration has become more acute, as the demand for high quality, relatively inexpensive color images, and thus, color printers and copiers to produce them has increased. Various methods of means have been proposed and used but they have not been entirely satisfactory.
The following patents and applications may be relevant to various aspects of this invention: